#6-32 UNC Thread
Direct Answer
6-32 UNC is a numbered Unified Coarse machine screw thread with a major diameter of 0.1380 inches (3.505 mm) and 32 threads per inch (TPI). Requiring a #36 (0.1065 inch) tap drill, it is the universal standard for desktop PC case covers, power supplies, 3.5-inch hard drive mounting, and North American electrical wall outlet boxes.
Source: ANSI/ASME B1.1 / NEMA OS 1 / SFF-8301
Specs
| Nominal Major Diameter | 0.1380 in (3.505 mm) |
| Threads Per Inch (TPI) | 32 TPI (Coarse pitch: 0.794 mm) |
| Fine Pitch Equivalent | #6-40 UNF (0.635 mm pitch) |
| Tap Drill Size | #36 drill bit (0.1065 in / 2.71 mm) |
| Minor Diameter (Internal) | 0.1042 in (2.647 mm) |
| Tensile Stress Area | 0.00909 in² (5.86 mm²) |
| Common Drive Size | PH2 / 1/4" Hex (6.35 mm) |
Desktop PC Fastening Dominance
6-32 screws (typically 1/4" hex head with integrated Phillips drive) are the standard fastener across desktop computer hardware:
- PC Case Covers & Expansion Slots: Secures side panels (thumbscrews) and PCIe expansion card brackets.
- Power Supplies (PSU): Mandated by ATX specification to mount PSUs to the chassis rear.
- 3.5-Inch Hard Drives: Mandated by SFF-8301 to mount 3.5" HDDs (in contrast, 2.5" SSDs use M2.5 or M3 screws).
- Motherboard Standoffs: Many case manufacturers (Antec, Corsair, Fractal) use #6-32 male/female motherboard standoffs.
US Electrical Receptacle Box Standard
In North American residential construction (NEMA OS 1), standard light switches, duplex outlets, and GFCI receptacles are secured to metal or plastic junction boxes using 1-inch long #6-32 oval-head screws.